foreach my $path ("/a/b/c/d/../../../e" , "/a/../b/./c//d") {
    my @c= reverse split m@/@, $path;
    my @c_new;
    while (@c) {
        my $component= shift @c;
        next unless length($component);
        if ($component eq ".") { next; }
        if ($component eq "..") { 
            my $i=0;
            while ($c[$i] =~ m/^\.{0,2}$/) {
                $i++
            }
            splice(@c, $i, 1);
            next 
        }
        push @c_new, $component;
    }
    print "/".join("/", reverse @c_new) ."\n";
}